1. Field of the Invention
The present invention relates to novel chemical compounds, and more specifically, it relates to a new class of phthalein dyes.
2. Background of the Invention
Various classes of phthalein dyes are known including phthaleins derived from heterocyclic compounds, such as, indoles and carbazoles and phthaleins derived from aminosubstituted and hydroxy-substituted carbocyclic aryl compounds, such as, anilines and notably phenols. Typically, these dyes possess spectral absorption characteristics alterable in response to changes in the pH of their environment and have found a number of different uses based upon their ability to change from one color to another, from colorless to colored and vice versa.
The present invention is concerned with a new class of phthalein dyes, namely, phthaleins including both phthalides and naphthalides derived from indolines.